Bi-fold door



FIG. 1 is a front perspective view of a bi-fold door according to a first version of our design;

FIG. 2 is a front elevational view, with the rear view being a mirror image thereof;

FIG. 3 is a front perspective view of a bi-fold door according to a second version of our design; and,

FIG. 4 is a front elevational view, with the rear view being a mirror image thereof.

The broken lines depict portions of the bi-fold door that form no part of the claimed design. 

CLAIM The ornamental design for a bi-fold door, as shown and described. 